The inventor began the study of laser amplifiers in 1962 as a means of generating powerful laser beams to study photo-photon and photon-particle interactions (Nature, May 1963). It soon became clear that the required laser amplifier had to be of the exponential form (Applied Optics 1967) in order to maintain laser beam amplification at a constant intensity and to minimise self-focussing effects within the laser amplifier medium. To avoid thermally induced distortions of the exponential amplifier medium and also to facilitate its optical excitation, it was necessary to segment the laser medium.
It was found that this could be done in two ways either parallel to the direction of propagation of the laser beam or perpendicular to said propagation direction. It was discovered that parallel segmentation of the exponential amplifier could best be achieved via the use of optical fibres and one of the earliest experiments utilizing optical fibres for this task were undertaken by the inventor at the Royal Radar Establishment, Malvern, UK in 1963, an effort which eventually led to the classification of the inventor's phased-array laser amplifier system by the U.S. Patent Office in August 1984.
By segmenting the exponential amplifier (Applied Optics 1967) perpendicular to the direction of the laser beam, solid slabs of lasing medium resulted which led to the folded, active mirror exponential amplifier described in two United States patents issued during the 1970's.
These prior art, segmented exponential laser amplifier inventions were designed specifically for the production of very high peak power laser outputs exciting 10.sup.15 watts per pulse for the study of photon-photon and photon-particle interaction physics. The present invention is designed specifically for compact slab laser systems for use in medical applications and industrial applications in particular where laser beams both pulsed and continuous wave are required at much more modest power levels.
The inventor has pursued the experimental study of associated technologies since 1963 and has been successful in operating open cavity single slab amplifiers of various dimensions up to 100 mm.times.20 mm.times.7.5 mm all flashtube excited.